Four House Democrats are the first to Join Republican critics raising alarm bells about the biggest change to bank accounting in decades.

The Democrats—Vicente Gonzalez and Henry Cuellar of Texas, David Scott of Georgia, and Brad Sherman of California—with 21 Republican House members wrote a May 6 letter to the Securities and Exchange Commission calling on the market regulator to study the effects of the current expected credit losses (CECL) accounting standard before publicly traded banks must start following it in 2020.

The lawmakers said they are concerned with how the rules would work in a...